As an integrated circuit ages, the operational characteristics of the circuit slowly change, which in turn affects the signals generated or manipulated by the circuit. For example, the duty cycle of a clock signal at a particular frequency may change due to circuit aging effects, or the timing relationship between two or more signals may change due to circuit aging. The aging characteristics of an integrated circuit are dependent on a variety of factors. These factors include device fabrication attributes, environmental conditions, and operating parameters. Device fabrication attributes include aspects of the integrated circuit fabrication process that influence aging. Environmental conditions include the ambient temperature at which the integrated circuit is operated, which in turn may determine the circuit temperature. Functional parameters include, for example, the voltage at which the circuit is operated.